Protective system for protecting buildings against aircraft crashes

ABSTRACT

A protective system for protecting a building from aircraft crashes and similar high-energy impacts includes a three-dimensional protective grid erected in front of a building wall at a distance therefrom and having interconnected beams. The protective system is supported on the building wall by a plurality of plastically deformable energy-absorbing elements and is therefore constructed in such a way that even an impact by a heavy four-jet engine aircraft, such as a Boeing 747 or Airbus A380, does not destroy the integrity of the building it protects.

CROSS-REFERENCE TO RELATED APPLICATION

This is a continuation application, under 35 U.S.C. § 120, of copending International Application PCT/EP2018/052974, filed Feb. 6, 2018, which designated the United States; this application also claims the priority, under 35 U.S.C. § 119, of German Patent Application DE 10 2017 201 915.8, filed Feb. 7, 2017; the prior applications are herewith incorporated by reference in their entirety.

BACKGROUND OF THE INVENTION Field of the Invention

The invention relates to a protective system for protecting a building against aircraft crashes and similar high-energy impacts of large-volume objects, including a three-dimensional protective grid erected in front of a building wall at a distance therefrom and having interconnected beams.

Such a protective system is known in the art from German Patent DE 10 2010 037 202 B4 of Hochtief Construction AG. In that specification, a protective sheath for protecting a structure from being struck by flying objects is situated at a distance from the outer envelope of the structure and is in the form of a grid, the grid bars of the sheath are formed at least partially of steel, the protective sheath is in the form of a self-supporting support structure, and the protective sheath is either not connected to the outer envelope of the structure at all, or is not connected to it through supporting elements.

SUMMARY OF THE INVENTION

It is accordingly an object of the invention to provide a protective system for protecting buildings against aircraft crashes, which overcomes the hereinafore-mentioned disadvantages of the heretofore-known systems of this general type in such a way that even an impact by a heavy four-jet engine aircraft such as a Boeing 747 or Airbus A380 will not destroy the integrity of the protected building.

With the foregoing and other objects in view there is provided, in accordance with the invention, a protective system for protecting a building from aircraft crashes and similar high-energy impacts, comprising a three-dimensional protective grid constructed or erected in front of a building wall at a distance therefrom and including interconnected beams. The protective grid is supported on the building wall through a plurality of plastically deformable, energy-absorbing elements, wherein each energy-absorbing element includes a steel tube disposed between the protective grid and the building wall in such a way that the force transmitted to the protective grid when an aircraft strike occurs acts on the tube at least predominantly in the radial direction and squeezes it together in cross-section.

Accordingly, it is important to the invention that the protective grid is supported on the building wall by a plurality of plastically deformable, energy-absorbing elements—and preferably exclusively by such elements. In addition, advantageously, the grid is supported by the ground.

The invention arises from the consideration that it is desirable to support the protective grid on the building wall in order to better distribute the impact loads, departing from the technical teaching disclosed in German Patent DE 10 2010 037 202 B4. As has been recognized in the context of the present invention, a portion of these loads may and should be absorbed by the protected building itself, to the extent that the building's structure is able to withstand or tolerate them without being catastrophically damaged. For this purpose, the transfer of force, pressure and deformation energy into the building wall is damped by using energy-absorbing and vibration-absorbing (damping) elements.

Advantageously, the respective energy-absorbing element includes a steel tube disposed between the protective grid and the building wall in such a way that the force transmitted to the protective grid upon impact of an aircraft acts on the tube at least predominantly in the radial direction and squeezes the tube together in cross-section. In contrast to ordinary shock absorbers that have a cylindrical shape and are installed in such a way that when placed under load they are resiliently compressed in the longitudinal direction, a predominantly plastic nonlinear deformation occurs in this case as a result of a force that acts on tube circumference or periphery in the radial direction. In order to increase energy dissipation, the tube may have a core or an installation made of crossed steel plates in the tube interior.

Through the use of numerical simulations, it has proven possible to show that the aforementioned energy-absorbing elements make a decisive contribution of up to 60% of the total energy dissipation through the protective system according to the invention, and considerably minimize the impact-induced vibrations in the building.

Advantageously, the protective grid includes an inner grid plane disposed parallel to the building wall and formed of steel beams and an outer grid plane disposed parallel thereto and formed of steel beams, the inner grid plane and outer grid plane being interconnected by steel beams.

In a preferred configuration, both the inner grid plane and the outer grid plane include a regular rectangular grid, the elementary cells of which have the same dimensions and are shifted from one another by half a lattice constant in at least one main direction of the grid. In this case, it is preferred that the inner grid plane and outer grid plane are connected to each other by diagonal beams, each of which extends from a node of one grid plane to a node of the other grid plane.

Other features which are considered as characteristic for the invention are set forth in the appended claims. Further advantageous configurations may be found in the dependent claims and in the following detailed description.

Although the invention is illustrated and described herein as embodied in a protective system for protecting buildings against aircraft crashes, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.

The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 is a diagrammatic, perspective view of a protective system installed in front of a building wall to protect the building from aircraft crashes;

FIG. 2 includes a top-plan view of the protective system according to arrow I in FIG. 1, below that a front-elevational view according to arrow II in FIG. 1 and below that a cross-sectional (side view) taken along a line A-A in FIG. 2;

FIG. 3 is an enlarged top-plan view of the protective system; and

FIG. 4 is a cross-sectional view through a tube that serves as an energy-absorbing fastening between the protective system and a building wall, shown above, by itself, and below, as installed in the protective system.

DETAILED DESCRIPTION OF THE INVENTION

Referring now in detail to the figures of the drawings showing a diagrammatic, simplified representation of an exemplary embodiment, in which parts that are identical or equivalent are given the same reference signs, and first, particularly, to FIG. 1 thereof, there is seen a protective system 20 with a protective grid 22 that is set up in front of a building wall 24 or another section of a building envelope, in the manner of a protective cover. The protective system 20 protects against aircraft crashes or similar high-energy and large-scale impacts of rockets, components or debris as a result of strikes, explosions, hurricanes and the like.

The protective grid 22 is formed from interconnected, in particular welded (steel) beams or struts or grid bars and includes a first grid plane that faces the building wall, which is also referred to as the inner grid plane E1, and a second grid plane that faces away from the building wall, which is also referred to as the outer grid plane E2. Each of the two grid planes E1, E2 is formed by interconnected longitudinal beams and transverse beams, which preferably span a regular surface grid. The two grid planes E1, E2 are interconnected by beams disposed between them, in particular by diagonal beams, so that overall, a three-dimensional space grid is realized.

In the example shown herein, it is assumed that the protected section of the building wall 24 spans a vertical plane above the ground 26. The inner grid plane E1 is disposed parallel to the building wall 24, forming a space or gap 28 having a gap width (=distance) a. Likewise, the outer grid plane E2 is disposed parallel to the building wall 24, and thus also parallel to the inner grid plane E1. The two grid planes E1, E2 thus form vertical planes spaced apart by a distance b.

As already mentioned, the outer grid plane E2 is realized by a plurality of longitudinal and transverse beams that are interconnected at intersections or nodes 30. In this example, the beams are vertical beams 1 and horizontal beams 3. The vertical beams 1 are disposed like columns, regularly spaced apart at an interval d, and are aligned vertically, which corresponds to how they are designated. The horizontal beams 3 running perpendicular to the vertical beams 1 are aligned horizontally, corresponding to how they are designated, and are disposed at regular distances h from each other, i.e. at different heights above each other. Preferably, the horizontal beams 3 and vertical beams 1 are fixedly connected, in particular welded, at each of the intersections or nodes 30. In this way, overall, a regular rectangular grid is created, the elementary cell of which has a width d and height h.

The inner grid plane E1 is constructed analogously to the outer grid plane E2. The inner grid plane thus likewise forms a regular rectangular grid of vertical beams 2 and horizontal beams 3′, the elementary cell of which preferably has the same width d and height h as the elementary cell of the outer grid plane E2. The distance between the two grid planes, i.e. the width or depth of the protective grid 22, is designated as b.

The two grid planes E1, E2 are advantageously not disposed congruently one behind the other starting from the front in a top view, but instead are shifted or offset relative to each other in the horizontal direction, i.e. in the longitudinal direction of the horizontal beams 3, 3′, preferably by half a grid width d/2. The nodes of the outer grid plane E2, when projected onto the inner grid plane E1, are thus located in the middle, between two nodes of the inner grid plane. In contrast, in the vertical direction, the two grid planes E1, E2 are preferably not shifted relative to each other, and thus a horizontal beam 3′ of the inner grid plane E1 is associated with a respective horizontal beam 3 of the outer grid plane E2 that is situated at the same height. This variant embodiment creates horizontal planes between the vertical grid planes E1 and E2, which may be used as floor areas. In an alternative embodiment, as shown in FIG. 1, the grid planes E1, E2 are offset by half a storey height h/2, and in this way, the vertical grid area is also made more compact.

As mentioned above, the two grid planes E1, E2 are interconnected by additional beams, which preferably are realized as diagonal beams 4, 5, and are connected to the nodes of the grid planes E1, E2, in particular by welding.

Specifically, in the exemplary embodiment of each node of the outer grid plane E2, four diagonal beams 4, 5 are connected to each associated node of the inner grid plane E1, except for some nodes that are disposed at the edge of the grid surface. Two of the four diagonal beams, namely those with reference sign 4, lie in a horizontal plane and extend to the two nearest nodes at the same height as the inner grid plane E1. The other two of the four diagonal beams, namely those with reference sign 5, extend in space diagonally, i.e. obliquely downward to the nodes of the inner grid plane E1 that are disposed directly below the aforementioned nodes (alternatively, they may also run diagonally upward, or there may be two diagonally upward-running diagonal beams in addition to the four mentioned diagonal beams). As a result, the four diagonal beams 4, 5 fan out from the respective node of the outer grid plane E2 in a quasi star-shaped or pyramid-shaped manner, corresponding to the offset of the two grid planes E1, E2 relative to each other, and establish the connection to the inner grid plane E1. As viewed from the nodes of the inner grid plane, the result is a mirror-image configuration. A triangular partitioning is observed from above (FIG. 3). Less than four diagonal beams may emanate from the edge nodes, due to their location on the periphery.

As is apparent from the top view of the protective grid 22 from above according to FIG. 3, the vertical beams 1 of the outer grid plane E2 are preferably all disposed on the same side of the horizontal beams 3, i.e. preferably on the inside, namely toward the building wall 24. The same applies to the inner grid plane E1, where the vertical beams 2 are disposed on the inside of the horizontal beams 3′.

The vertical beams 1, 2 are preferably manufactured integrally, i.e. as a single piece, and preferably have a double-T-shaped cross-section, or alternatively a rectangular cross-section. The same applies to the horizontal beams 3, 3′ and the diagonal beams 4, 5.

The beams are preferably dimensioned as follows with regard to their cross-sectional width B and their cross-sectional height H:

1, 2 Vertical beams W/H = 500-1000/500-1000 mm 3, 3′ Horizontal beams W/H = 500-1000/500-1000 mm 4 Diagonal beams (horizontal) W/H = 400-800/400-800 mm 5 Diagonal beams (diagonal) W/H = 400-800/400-800+ mm

Preferred materials for the beams are grades of steel having high ductility and plastic deformability.

The structural dimensioning of the protective grid 22 is preferably as follows:

Distance between vertical beams d = 10-15 m Distance between horizontal beams h = 5-10 m Width of protective grid b = 10-15 m Distance from protective grid to building wall a = 0.3-2.0 m

The overall height and width of the protective grid 22 is adapted to the dimensions of the building or building section to be protected.

The protective grid 22 is preferably constructed to be self-supporting and is advantageously supported on the ground 26 by using at least some, preferably all of the vertical beams 1, 2. The vertical beams 1, 2 are suitably anchored to the ground 26 and are grounded on a foundation. The vertical beams 1, 2 may therefore also be referred to as columns or supports.

In addition, the protective grid 22 is connected to the building wall 24 through a plurality of shock-absorbing or energy-absorbing elements or dampers 32. These energy-absorbing elements 32 are preferably tubes 6 or hollow cylinders made of steel, which are disposed between the protective grid 22 and the building wall 24 in such a way that upon impact of an object against the protective grid 22, they are compressed or squeezed and consequently plastically deformed from the front (impact direction substantially in the direction of arrow II in FIG. 1), perpendicular to their longitudinal axis, i.e. in the radial direction 34 when viewed in cross-section.

In a preferred installation variant, the respective tube 6 is disposed between the building wall 24 and the vertical beams 2 of the inner grid plane E1 facing the building wall 24, i.e. in the intervening gap 28. The tube diameter D is accordingly at most as large as the gap width a. The longitudinal axis of the tube 6 is preferably disposed to be vertical, i.e. parallel to the vertical beam 2. Preferably, the tube 6 is fixedly connected, in particular welded, to the associated vertical beam 2 on its outer circumference, and is also leaned against the building wall 24. In this case, the tube 6 represents an energy-absorbing (connecting) element or a bracket/fastening/suspension/support or bearing between the protective grid 22 and the building wall 24.

Alternatively, there may be a gap between the building wall 24 and the tube 6. In the latter case, it is more expedient to simply speak of an energy-absorbing element instead of an energy-absorbing support.

However, other installation variants are also possible in which the energy-absorbing tube 6, for example, is attached to a horizontal beam 3′ of the inner grid plane E1. In addition, a type of series or row configuration may be realized, with a plurality of parallel adjacent tubes disposed inside a gap 28 between the inner grid plane E1 and the building wall 24. The required tube length and configuration depends on the required energy absorption and the (expected) impact pulse.

In order to increase the energy absorption capacity, a plastically deformable core 36, which preferably is formed of cross-welded steel plates, is advantageously disposed in the respective tube 6. In the cross-sectional representation shown in FIG. 4, the core 36 forms a cross inside the circumference of the tube, and the center of the cross coincides with the longitudinal axis of the tube 6. The core 36 is preferably only clamped into the tube 6 and is not attached to the inner wall of the tube in any other way.

Preferred dimensions for tubes 6 that are used as energy-absorbing elements are as follows:

Tube diameter D = 300-1000 mm Wall thickness t = 10-25+ mm Thickness of plates in the core T = 10-50 mm

The dimensions given herein and further above are adapted to the requirements for protecting a nuclear power plant building against aircraft crashes, in particular by four-jet passenger aircraft, and have been verified in the context of numerical simulations. The dimensioning varies with the requirements in individual cases.

Preferred materials for the tubes 6 and cores 36 are grades of steel having high ductility and plastic deformability.

Since it is anchored to the foundation, part of the energy absorbed in the event of an impact or strike of an object on/into the protective grid 22 is diverted through the foot support. Another part of the energy is absorbed by the plastic deformation of the protective grid 22 itself and is distributed over a larger impact surface. In addition, a considerable part of the energy is absorbed by the energy-absorbing elements 32 that are nonlinearly deformed when the impact occurs, and only a small part of the energy is transferred to the building in a greatly attenuated form. This reduces the amount of energy transferred to the protected building to an acceptable level. In this way, it is ensured that the building is not structurally overloaded and that impact-related vibrations and oscillations are limited to an acceptable level. Finally, the protective grid 22 splits an impacting object into a plurality of small debris parts, which are deflected in different directions and hit different parts of the building wall 24 at reduced speed.

Furthermore, a particular advantage of the structure is that the entire building does not have to be converted. Instead, the protective cover may be spatially limited to the particularly vulnerable or sensitive sections of the building wall 24 or building envelope.

In an expedient modification of the above-described structure, the protective grid 22 may be mounted on the building wall 24 exclusively through the energy-absorbing elements 32, without support on the ground, which is useful, for example, for protecting ceiling sections. In this case, of course, the spatial position and orientation of the protective grid 22 must be adapted to the installation situation. This means that the “vertical beams” and “horizontal beams” are then oriented differently in space than has been described heretofore and suggested by the terminology used herein.

Finally, the shape of the protective grid 22 could potentially follow the outer contour of a building, for example a circular or otherwise curved outer perimeter of a dome-shaped power plant building. This is expediently achieved by straight sections as described above, with bends in between.

The mentioning of steel in the description above signifies that the component in question is formed at least partially of steel. This expressly includes composites of steel and other materials.

A particularly important field of application is the protection of power plant buildings or the building envelopes of nuclear power plants or other nuclear facilities. Of course, many other applications are also possible for protecting industrial plants or military objects from aircraft crashes and the like.

The following is a summary list of reference numerals and the corresponding structure used in the above description of the invention.

LIST OF REFERENCE SIGNS

-   1 Vertical beams -   2 Vertical beams -   3 Horizontal beams -   3′ Horizontal beams -   4 Diagonal beam -   5 Diagonal beam -   6 Tube -   20 Protective system -   22 Protective grid -   24 Building wall -   26 Ground -   28 Gap -   30 Node -   32 Energy-absorbing element -   34 Radial direction -   36 Core -   E1 Inner grid plane -   E2 Outer grid plane 

1. A protective system for protecting a building from aircraft crashes and similar high-energy impacts, the protective system comprising: a three-dimensional protective grid to be erected in front of and at a distance from a building wall, said protective grid including interconnected beams and a plurality of plastically deformable, energy-absorbing elements supporting said protective grid at the building wall; each of said energy-absorbing elements including a steel tube disposed between said protective grid and the building wall causing a force transmitted to said protective grid when an aircraft strike occurs to act on said tube at least predominantly in a radial direction and to squeeze said tube together in cross-section.
 2. The protective system according to claim 1, wherein said protective grid is supported on the building wall exclusively by said energy-absorbing elements.
 3. The protective system according to claim 1, wherein said tube has a diameter in a range between 0.3 and 1.0 m and a thickness in a range between 10 and 50 mm.
 4. The protective system according to claim 3, wherein said tube has a tube interior and a core formed of crossed steel plates disposed in said tube interior.
 5. The protective system according to claim 1, wherein said protective grid includes: an inner grid plane disposed parallel to the building wall and formed of steel beams; an outer grid plane disposed parallel to said an inner grid plane and formed of steel beams; and further steel beams interconnecting said inner grid plane and said outer grid plane.
 6. The protective system according to claim 5, wherein said inner grid plane and said outer grid plane are spaced apart by a distance in a range between 10 and 15 m.
 7. The protective system according to claim 5, wherein said inner grid plane and said outer grid plane each include a respective regular rectangular grid having elementary cells with identical dimensions, said elementary cells of said inner grid plane and said elementary cells of said outer grid plane being displaced relative to one another by half a lattice constant in at least one direction.
 8. The protective system according to claim 7, wherein said elementary cells have a width in a range between 10 and 15 m and a height in a range between 5 and 10 m.
 9. The protective system according to claim 7, wherein said inner grid plane and said outer grid plane each have respective nodes, and said further steel beams are diagonal beams respectively extending from a node of one of said grid planes to a node of another of said grid planes for interconnecting said inner grid plane and said outer grid plane.
 10. The protective system according to claim 1, wherein a plurality of said interconnected beams support said protective grid on the ground.
 11. The protective system according to claim 1, wherein said interconnected beams of said protective grid have a double-T or rectangular cross-section with dimensions in a range between 400 and 1000 mm.
 12. The protective system according to claim 1, wherein said protective grid is spaced apart from the building wall by a distance in a range between 0.3 and 2.0 m. 